@Sarah977
I totally get what you are saying. Personally, I do not do self check in anyway and I certainly do not want guests fiddling with heating controls. In fact, I ask them not to in my house rules.
However, I am a hands on homestay host, not someone who is managing a bunch of listings remotely. Also, a lot of people are really into smart tech these days. It's becoming much more commune so using Apps to manage things like lighting and heating is not unusual at all. Do I need it? No, not really, but some people are really into that stuff.
I have a colleague who uses Alexa, or something similar, to turn on and off all his lights and also adjust them from one colour to another as well as a bunch of other stuff, e.g. turn off the music, turn up the volume, open or close the blinds. It's not as unusual as someone like you or I (who maybe think all this is completely unnecessary) thinks.